Verlander in 2006 was decent in his rookie campaign. He pitched to contact for the most part and got a ton of outs and was effective. His 2007, he effectively threw the same amount of innings as the yr before, but his K rate rose significantly and led him to throw over 400 pitches more in that season. Come 2008, he was still searching for an identity and his arm was tired as evidenced by his career low 93.6mph average fastball. What happened the following yr? His arm rebounded and he added a slider and the rest is history.
Jon Lester, OTOH, crossed the 3000 pitch markin 2008 and hasnt looked back. If you are looking at this from a fatigue POV, you would have expected a dropoff in 2009, but you didnt see that. What you saw was sustained dominance through 2010. You saw a very strong 2011 and then a terrible 2012. Why might that have happened to a guy so young? Well, his FB velo is down nearly 1.5mph and his cutter velo is up over 1mph. The increased velo is taking away some of its bite and flattening it out at nearly the same speed on the same plane leading to it getting hit. You also are seeing his changeup increase in speed as well. You also are seeing a guy who cannot command his pitches in the zone anymore. While he may never recover his lost velocity, his other flaws are correctable assuming he doesnt be an obstinate ass and insist on doing things like Beckett did, alone and without input from anyone else. He is no longer a guy anyone considers as one of the elite pitchers in the game and likely won't return to that level of dominance, but he very well can return to a 200IP, 8K/9IP pitcher with an ERA around or below 4.